NOTE: Story is from Oct 2001 "Black holes may be worse monsters than we thought. Not only do they inexorably devour matter around them, but they may also be able to steadily belch out energy. This is the of conclusion a European-led team of astronomers whose work with ESA's XMM-Newton X-ray observatory has produced surprising new results."

"It corresponds to a theory proposed over 25 years ago by two Cambridge University astronomers. Roger Blandford and Roman Znajek had suggested that rotational energy could escape from a black hole when it is in a strong magnetic field which exerts a braking effect. This theory fits the physical laws of thermodynamics which state that energy released should be absorbed by the surrounding gas."

Also at NASA